Insulator bushing for electrical petroleum dehydrators



.1; M. CAGE Nov, 8, 1932.

.INSULATOR BUSHING FOR ELECTRICAL PETROLEUM DEHYDRATORS Filed Feb. 11,1950 Patented Nov. 8, 1932 UNITED STATES PATENT OFFICE JOHN M. CAGE, LOSANGELES, CALIFORNIA, ASSIGNOB, BY MESNE ASSIGNMENTS, TO ELECTRICSEPARATION COMPANY, LIMITED, OF NEW YORK, N. Y., A CORPORATION OFDELAWARE INSUIA'IOB BUSHING FOE ELECTRICAL PETROLEUM DEHYDRATOESApplication fled February 11, 1930. Serial No. 427,637.

This invention is concerned with insulator bushings such as are employedto convey a high potential electrical conductor through the wall of aclosed treater tank in the electrical dehydration of petroleumemulsions. While the present insulator bushing is not a limited inapplication to dehydrators, it has been especially designed to meet thepeculiar problems encountered in suiting an insulator bushing to suchuse, and will therefore be described in that particular association, butwithout necessary limitation thereto.

In the art of electrically dehydrating petroleum emulsions of water andOil, the emulsion is flowed through a closed treater tank in which isprovided a live inner electrode insulated from the tank and energized bymeans of an electrical conductor passing through an insulator bushingsuitably mounted in a wall of the tank. The wall of the tank may itselfform the outer or grounded electrode. The emulsion upon coming withinthe influence of the charged inner electrode gives up its water, theemulsified water particles tending to coalesce and sinking in relativelylarge bodies to the bottom of the tank, where the water is withdrawn.The dried oil rises and is delivered from the top of the tank.

One of the greatest sources of trouble in the operation of electricalpetroleum dehydrators of this nature resides in the insulator bushing,the dielectric material of which 15 under constant liability of breakingdown under the severe strains exerted upon it. The nature of thesebushing failures is often a fracture or complete breaking off of thedielectric tubes of which the bushing is composed. The best bushingsproduced by the art to date, in fact, last not more than a comparativelyfew hours under the operating conditions which I have found best inpoint of dehydration effectiveness. And each time the bushing so breaksdown, which is thus at comparatively frequent intervals, dehydrationoperations must be suspended for several hours while a'new bushing isinstalled. The costs involved in the loss of production forced byrelatively frequent shutdowns of this kind fer to operate my dehydratorat a temperature of around 200 F and at a potential of 60 to 100,000volts; and under these conditions breakdown of the best bushing of thistype heretofore available may occur in from one to thirty six hours.

As the conclusion drawn from a number of experiments which I haveconducted, I attribute the breaking of the bushin s to a combination oftwo separate causes, rst, to too high a potential stress being permittedto exist over and through the porcelain tubes, and second, to theinability of the bushing, as heretobefore constructed, to expand withthe heat of the emulsion without great internal stresses being set up,the action probably being that the porcelain tubes and the interveninglayers of cement expand at diiferent rates and therefore cause theporcelain tubes to be subjected to severe internal stresses, which oftencause their fracture.

It is the object of the present invention to provide a bushing adaptedto withstand severe operating conditions, both as regards heating andthe application of high electrical potential.

To prevent the bushings from breaking in the presence of heat, I nowfill the annular spaces between the tubes with a fluid such as oil, asmall ring portion of cement being provided at the ends of the tubes tospace the tubes properly and to seal the oil in at the bottom, butthisamount of cement alone not being capable of exerting sufficient force onthe tubes to cause fracture thereof. The oil is free to circulatethrough oil passages provided in the other end of the bushin so that itcan flow back and forth out of an into the annular inter-tube spaces asthe bushing expands andcontracts with changing temperatures.

To guard against breakdown due to high potential stresses, I equip thebushing with certain shields which tend to draw the dielectric fieldaway from the surface of the bushing, and also which prevent stressconcentra tion through the dielectric material of the bushing, but theseprovisions may be discussed to better advantage in the body of thespecification. Further, the above described oil filling in the annularspaces between the dielectric tubes increases the dielectric strength ofthe bushing and therefore decreases the liability of break-down byreason of dielectric failure.

The invention will best be understood from the following detaileddescription of a present preferred embodiment thereof, reference forthis purpose being had .to the accompany= ing drawing, in which:

Fig. 1 is a vertical medial section through a dehydrator typifying theapplication of my bushing;

Fig. 2 is a longitudinal medial section of m bushing; and

Fig. 3 is a transverse section taken on line 33 of Fig. 2.

Referring now to the drawing, and particularly to Fig. 1, I show at 10 asuitable shell or tank closed at the top with a dome 11, and having abottom 12. Provided in the side of the tank is an emulsion inlet pipe13, which discharges tangentially below a conical baflie plate 14, theincoming emulsion flowing more or less spirally upward from under itslower edge. A pipe 16 withdraws water from the bottom of the tank. Thecleaned oil outlet is located in the dome of the tank, as at 17.

A cylindric shell 18 is carried in the top of the tank, its lower edgeextending just below dome 11 and carrying a conical baflie plate 19extending downwardly into the tank, as shown in the drawing. Theinsulator bushing, indicated generally at 20, is provided with anintermediate mounting flange 21 which rests upon and is fastened down toan inturned flange 22 provided in shell 18. The bushing and theoverlappin flanges 21 and1 22 thus close the upper end 0 the treater tanThe insulator bushing 20 (see Fig. 2) em 34 annularly spaced from theintermediate tube 32. s

' The intermediate tube is connected at its lower end to the inside tubeby a short layer or ring 35 of some suitable cement, for inspaces 43closed at the ends cement. These open spaces are sealed off at stancelithar e, and at its upper end by another short ayer 36 of cement, theupper layer, however, being perforated with a number of oil passages 38(see Fig. 3). Similarly, the outside tube is connected at its lower endto the intermediate tube by a short layer 39 of cement, and at its upperend by another layer40 of cement, which is perforated as at 41 for thepassage of oil. These short upper and lower layers or rings of cementannularly space the tubes, and there is thus provided between the tubeslon annular open by the rings of the bottom by the cement, but are openat the top through the perforations 38 and 41, re-

spectively. The rod conductor 31 closely fits the central opening of theinside tube 30 only at the ends thereof, being reduced along its centralsection 31a to provide another longitudinally extendingannular 0 en sace 43, which is adjacent the inner sur ace 0 the inside tube 30. Theupper end of the conductor 31 is then provided with an oil passage 47whereby oil may flow into the last described annular space 43.

The mounting flange 21 of the bushing is secured to the outer surface ofa shield member 44 in the form of an outwardly flared plate, theshielding function of which will be set forth later, and for support ofthe bushing the member 44 is connected to the outside tu e 34 by meansof a layer of cement 45.

Referring now to Fig. 1, theportion of the bushing above flange 21extends upwardly in shell 18, while the portion below the flange!extends downwardly into the treater, terminating somewhat short of thelower limit of the conical bafile plate 19. Shell 18 is closed at thetop, and has in its side wall an There is preferably provided on theupper 'end of conductor 31 adjacent the upper end ofthe bushing severallayers of insulatin board 53, and above this insulating materia 53 ametal plate 54 having at its outer edge a shield ring 55, which isspaced from the side walls of shell 18 by a determined distance. Thefunction of this insulating material 53 and ring 54 will be set forthlater.

The upper bushing compartment 57 provided by shell 18 is filled with asuitable dielectric fluid such as transformer oil, and this oil runsdown through the perforations 38 and 41 in the cement at the tops of theinsulator tubes, and through the passage 47 in the top of the conductor31, and thus enters the 1ongitudinally extending annular spaces 43between and within the said tubes, which spaces 'the oil fillscompletely. There is thus provided an oil filling in the spaces betweenand within the tubes which can flow back and forth through the oilpassages provided at the upper end of the bushing, and in this wayinternal stresses due to expansion of the intertube filling material arepositively precluded. The short rings of cement used only at the ends ofthe tubes are not of themselves capable of setting up sufiicientstresses to fracture the porcelain. it will be noted that since the oilpassages are at the top of the annular spaces, the oil runs downwardlyin originally entering these spaces and displaces the air thereinupwardly, which all leaves by way of the oil passages. There is thusprovided positive assurance that all of the air originally presentwithin the tubes is displaced by the oil.

Connected to the bushing conductor 31 just below the lower end of thebushing is the inner or live electrode 60, which embodies in the presentinstance a metal rod of about two and one-half inches in diameter andextending downwardly in the tank to a suitable distance below the lowerlimit of the conical baflie plate 19. This electrode is energized orcharged through the conductor 51 leading through bushing 50 to theconductor 31 which runs through the main bushing 20, conductor 51 beingunderstood to be connected to one side of the secondary of a suitablehigh-tension transformer, not illustrated. The tank itself is groundedto form the outside or grounded electrode.

A shield ring 61 is carried by the rod electrode just below theinsulator bushing and above the lower edge of the conical baflie plate19, and spaced from ring 61 and carried by a plate 62 extending frombaflle 19 is a second ring 68. The manner in which these shieldingprovisions protect the bushing against electrical stresses will bediscussed at a later point in the specification.

In the operation of the dehydrator, the wet emulsion is delivered to thetank in heated condition through the inlet 13 below baflle 14. Fromthere the emulsion passes upwardly and into the zone about the electrode26, where it is subjected to electrical influence and separates intocomparatively dry oil and water. The separated water sinks to the bottomof the tank, where it is withdrawn by means of pipe 16; while thecleaned oil rises and is discharged from the top of the tank at 17. Abody of inert gas trapped Within the open-bottomed compartment 65provided by bafile plate 19, prevents rise of the emulsion therein andin this way maintains the surface of the bushing in a clean andnonconductive condition.

The shield ring 61 which I provide on the rod electrode just below theinsulator bushing, is described and claimed in my copending applicationentitled Dehydrator construction, filed August 8, 1928, Ser. No. 289,-

174. As there set forth, its function is to provide a path for thedielectric field from throu h which the electrica the live electrode tothe grounded tank which is of lesser resistance than that directly overthe surface of the bushing to the tank. Thus, the spaced rings 61 and 63providing a path stress is accordingly eavily concentrated, the stressover the surface of the bushing and the liability of conductionthereover is reduced to a minimum. The upper ring 55 which is rovided onthe conductor 31 just above the ushing, has a similar function,providing a path from the conductor through the transformer oil in thecompartment to the shell 18 which is of lower dielectric stren th thanthe path over the surface of the bus ing to the shell. The insulatingmaterial 53 increases the length of the latter path, and hence decreasesthe liability of current flow thereover. The result of this provision isagain that the dielectric stress between the live conductor and thegrounded shell is heavily concentrated in a path removed from thesurface of the bushing, which is thereby greatly relieved of stress.

The outwardly flared shield 44 to which the mounting flange 21 of thebushing is secured, has a smooth interior surface 44a within which thebushing is cemented. The shield is comparatively wide, and being ofsmooth contour distributes the dielectric stress between the flange 21and the porcelain tubes of the bushing overa relatively wide area,thereby decreasing materially the dielectric stress density through theorcelain, and decreasing in a like measure t e liability of the bushingto break down at this point.

Thus it will be seen that my shielding pmvisions largely relieve thebushing of the high-density dielectric stresses to which it hasheretofore been subjected.

Moreover, the oil filling in the annular spaces between the tubesincreases the dielectric strength of the bushing, and therefore,decreases the liability of the bushing failing under the potentialstresses to which it'is subjected.

One of the chief advantages of the present bushing, however, resides inthe means for relieving the porcelain tubes of internal stresses set updue to thermal expansion. The oil that fills the annular inter-tubespaces is free to be expelled from the bushin as the oil increases involume with increase tempera.- ture, and there is therefore nopossibility of a pressure exerted upon the tubes due to ex-- pansion ofthe filling material therebetween, as in prior bushings.

The bushing provided by the present invention stands up indefinitelyunder the most severe operating conditipns, and has done away entirelywith the frequent shut-downs heretobefore necessitated by frequentbushing failures.

It will be understood that various changes in the design, structure andarrangement of m herein described provisions may be'made withoutdeparting from the spirit and scope of my invention, which is only to belimited as defined in the following chums. Y

I claim 1. In combination leum dehydrator involving a treater tank,

7 vertical walls defining a compartment opening into the upper end ofsaid treater tank, ng connected near its center an insulator bus 1portion, and forming a barrier, in the lower portion of saidcompartment, said com art- 7 end of the bushing extending ownwardly inment adapted to contain insulating oil a ove said bushing, said bushinginvolving annularly spaced dielectric tubes, and the annular spacesbetween said tubes bein closed at the the tank but open at the end ofthe bushing insulator bushing in the wall of sai insulatextendingupwardly into said compartment,

whereby oil in said compartment may circulate into and out of saidannular aces, an

ing oil containing compartment, and an electnc bushings to reach theinterior of the tank.

, y 2- In combination in an electrical petroleum dehydrator involving atreater tank, vertical walls definin artment opening a comp treatertank, an

into the upper en of sai "insulator bushing connected near its centerportion, and forming a barrier, in the lower portion of-saidcompartment, said com artment adapted to contain insulating oila ve 1yspaced a said bushm said bushing involving annular electric tubes, andthe annular spaces between said tubes bein closed at the end'of thebushing extendin ownwardly' in the tank but open at the en of thebushing extending upwardly into said compartment, whereby oil in saidcompartment may circulate into and out of said annular spaces, and anelectrical conductor passing through said 'insulatin oil containingcompartment and hereunto subscribed my name this 'said ins ator bushingto reach the interior of the tank.

' In witness that I claim the fore in 225 day of January 1930. v

" GAGE.

electrical petroal conductor passing in turn through the; last mentionedand first mentioned insulator Ihave

